Create the array, and then populate it:

something[] manytypes = new something[2];
for (int i=0; i < manytypes.Length; i++)
{
   manytypes[i] = new something(2, 4.305);
}

With a relatively small number of array elements, it's simple enough to  
write:

    something[] manytypes = { new something(2, 4.305), new something(2,  
4.305) };

Of course, while more lengthy for small numbers of elements, it'd be more  
maintainable to write:

    something[] manytypes = new something[2];

    for (int i = 0; i < manytypes.Length; i++)
    {
        manytypes[i] = new something(2, 4.305);
    }

And for longer arrays, that's actually likely to be easier.

And of course, if the "something" class is immutable, you could even write:

    something init = new something(2, 4.305);
    something[] manytypes = new something[2];

    for (int i = 0; i < manytypes.Length; i++)
    {
        manytypes[i] = init;
    }

That would be more efficient than creating a new instance of the class for  
each array element.

Pete